70 MR. J. SMITH ON THE ORIGIN OF COLOUR 



rather to produce great intervals between vibrations, in 

 order to obtain good colours. The plan often adopted was 

 to take a whole disc, paint one half of it completely black, 

 and treat the other half in the manner required. By this 

 means I obtained longer intervals between one vibration 

 and another, and saved time in experimenting, that is in 

 making discs. 



106. Definite ratios of white and black give distinct co- 

 lours, because the beats or vibrations are distinct. When 

 the discs are made to revolve with a small degree of 

 excentricity the colours are still distinct, but some of the 

 rings of colour become compounded. When, however, 

 the excentricity is great there is great confusion of colour, 

 proving as I think the comparatively long interval be- 

 tween one vibration and another in nature, in order to 

 produce a distinct impression of colour on the sensorium. 



{See plate IV. figs. 8 and 9.) 



107. Sunlight is much more inconstant in its effects 

 than gaslight, although the state of the atmosphere has 

 a very decided influence even on gaslight as any one who 

 experiments as I have done will find. In gaslight, 



a ring \ white | black produces green or purple. 

 „ 3 ?j I „ „ another green or purple. 



„ I ,, i „ „ yellow. 



A narrow black line in one direction of the light gives a 

 bright red, in another direction green, whilst in sunlight 

 the lines produce a mauve or an olive green, according to 

 the light or the velocity given to the figure. 



But I am unwilling to indicate the numerical value of 

 any colour at present. The subject requires much more 

 study than I have hitherto been able to give to it, so as to 

 yield satisfactory results. 



